Good question. Not one to give up, so tried a few things on the Warbird, today. I switched to a shorter stem, raised the angle of the handlebars to better reach the hoods and moved the seat forward, a bit. I then did the same 10 mile ride after my MTB workout.

It did seem to help. No back pain when I got home, though still some numbness. Noticeably reduced hand numbness, too. Probably on the right path, since my average speed improved, too. Even did a little half mile of sandy road to practice dealing with fishtailing in the soft stuff, which is a must for riding a 700x35 bike on gravel and that, after all, is what the Warbird is designed to do. I like the bike and have put a lot of work into it. Jury is still out on this one.

My Trek Domane WSD, though, should go to someone who will use it, so it will get sold or traded. The Warbird does equally well on pavement, but can also go off pavement, which, of course, the Domane cannot. A pavement only bike is just not very useful for my riding.